[c#] How to get the last five characters of a string using Substring() in C#?

I can get the first three characters with the function below.

However, how can I get the output of the last five characters ("Three") with the Substring() function? Or will another string function have to be used?

static void Main()
{
    string input = "OneTwoThree";

    // Get first three characters
    string sub = input.Substring(0, 3);
    Console.WriteLine("Substring: {0}", sub); // Output One. 
}

e.g.

string str = null;
string retString = null;
str = "This is substring test";
retString = str.Substring(8, 9);

This return "substring"

C# substring sample source

Substring. This method extracts strings. It requires the location of the substring (a start index, a length). It then returns a new string with the characters in that range.

See a small example :

string input = "OneTwoThree";
// Get first three characters.
string sub = input.Substring(0, 3);
Console.WriteLine("Substring: {0}", sub);

Output : Substring: One

Here is a quick extension method you can use that mimics PHP syntax. Include AssemblyName.Extensions to the code file you are using the extension in.

Then you could call:

input.SubstringReverse(-5) and it will return "Three".

namespace AssemblyName.Extensions {

    public static class StringExtensions
    {
        /// <summary>
        /// Takes a negative integer - counts back from the end of the string.
        /// </summary>
        /// <param name="str"></param>
        /// <param name="length"></param>
        public static string SubstringReverse(this string str, int length)
        {
            if (length > 0) 
            {
                throw new ArgumentOutOfRangeException("Length must be less than zero.");
            }

            if (str.Length < Math.Abs(length))
            {
                throw new ArgumentOutOfRangeException("Length cannot be greater than the length of the string.");
            }

            return str.Substring((str.Length + length), Math.Abs(length));
        }
    }
}

If you can use extension methods, this will do it in a safe way regardless of string length:

public static string Right(this string text, int maxLength)
{
    if (string.IsNullOrEmpty(text) || maxLength <= 0)
    {
        return string.Empty;
    }

    if (maxLength < text.Length)
    {
        return text.Substring(text.Length - maxLength);
    }

    return text;
}

And to use it:

string sub = input.Right(5);

static void Main()
    {
        string input = "OneTwoThree";

            //Get last 5 characters
        string sub = input.Substring(6);
        Console.WriteLine("Substring: {0}", sub); // Output Three. 
    }

• Substring(0, 3) - Returns substring of first 3 chars. //One

• Substring(3, 3) - Returns substring of second 3 chars. //Two

• Substring(6) - Returns substring of all chars after first 6. //Three

string input = "OneTwoThree";
(if input.length >5)
{
string str=input.substring(input.length-5,5);
}

In C# 8.0 and later you can use [^5..] to get the last five characters combined with a ? operator to avoid a potential ArgumentOutOfRangeException.

string input1 = "0123456789";
string input2 = "0123";
Console.WriteLine(input1.Length >= 5 ? input1[^5..] : input1); //returns 56789
Console.WriteLine(input2.Length >= 5 ? input2[^5..] : input2); //returns 0123

index-from-end-operator and range-operator

One way is to use the Length property of the string as part of the input to Substring:

string sub = input.Substring(input.Length - 5); // Retrieves the last 5 characters of input

// Get first three characters
string sub = input.Substring(0, 3);
Console.WriteLine("Substring: {0}", sub); // Output One. 

string sub = input.Substring(6, 5);
Console.WriteLine("Substring: {0}", sub); //You'll get output: Three

string sub = input.Substring(input.Length - 5);

simple way to do this in one line of code would be this

string sub = input.Substring(input.Length > 5 ? input.Length - 5 : 0);

and here some informations about Operator ? :